This project consists of the implementation and evaluation of a developmentally based, long-term, comprehensive intervention designed to prevent conduct disorder and social maladaptation in adolescence and adulthood. The hypotheses will be tested that such an intervention will lead to proximal improvements in child behavior and family ecology and, in turn, that these changes will lead to the long-term prevention of conduct disorder. The project will be carried out at four sites (Durham, NC/Duke, Nashville, TN/Vanderbilt, rural Pennsylvania/Penn State, and Seattle, WA/U. of Washington) with three successive cohorts of children who will be followed over 12 years. Kindergarten-age children who are at high risk for conduct disorder will be randomly assigned to an intervention (child n = 480) or control (child n = 480) group. The initial two-year-long intervention will attempt to promote children's compliant behavior, so- cial-cognitive skills, peer relations, and academic success; to promote parents' and teachers' skills in child behavioral management; to assist teachers in promoting children's social competence; and to develop coordination between families and schools. Effects of intervention will be evaluated in multiple theoretically based ways. In addition, a randomly selected group of low-risk children in both intervention and control schools will be followed to examine possible effects of intervention as well as risk factors in the development of conduct disorder. In the proposed three-year grant period, intervention will focus on the developmental period of school entry (grades 1 and 2). Further preventive intervention and evaluation is planned for the transition to middle school and early adolescence in a subsequent grant period.